Modern hair dyeing methodology has developed from its initiation in the 1950's to the point where, today it is the third largest product type in the hair care category following shampoos and conditioners.
The most commonly used method of dyeing hair, particularly human hair, is oxidative dyeing in which a mixture of aromatic compounds, generally of the benzenoid series, containing a plurality of nuclear amino and hydroxy functions, and which are themselves colorless, are converted by coupling reactions well known to those skilled in the art to a blend of colored compounds within the hair fibers by oxidative processes. The colorless aromatic compounds, in a suitable base formulation, normally are mixed with hydrogen peroxide or other strong oxidizing agent shortly before use. The colored compounds or dyes are, typically, formed by oxidative coupling between primary intermediates (usually diamino benzenes or amino phenols) and couplers which are phenols or related cyclic compounds. Various shades are developed by using a mixture containing more than one of both the intermediate and the coupler.
The intermediates and couplers because of their low molecular weights and water solubility diffuse easily into the hair where the coupling reaction takes place. The colored products developed by oxidation, however, remain trapped in the hair by virtue of their higher molecular weights, relative insolubility in water and absorptive affinity to the internal hair surface. This is the basis for permanent tints and toners which, ideally, last for the life of the hair and are relatively unaffected by shampooing and perspiration. Although permanence is the desideratum of the hair colorist, in practice it is difficult to achieve.
Another type of hair dyeing is direct dyeing in which the dye is deposited, and colors the keratinous fibers. Typical direct dyes include, for example, nitroaminophenols, nitrophenylenediamines, azo dyes, anthraquinones and nitroaminophenylethers.
One of the chief disadvantages of conventional oxidative dyeing is that the oxidant most often used is hydrogen peroxide. Although this chemical has the advantage of being harmless to the skin and inexpensive, it has the severe disadvantage of destructively oxidizing the hair keratin, causing oxidative and bleaching damage to the hair.
Moreover, hydrogen peroxide is normally used under alkaline conditions using ammonia or an amine as the alkaline reagent. These bases impart strong odors to the hair dyeing compositions to which many users strongly object.
Other oxidants have been suggested in attempts to avoid the problems of using hydrogen peroxide.
For example U.S. Pat. No. 2,944,869 teaches the use of orthophenols with alkali metal iodates, periodates and persulfates to form color in hair. U.S. Pat. No. 3,698,852 suggests that combinations of DOPA derivatives and arylamine derivatives in mixture with alkaline H.sub.2 O.sub.2 dyes hair permanently. The patent also teaches that chlorate (ClO.sub.3.sup.-) salts can be employed with or without peroxide. It is required that the couplers be catechols.
U.S. Pat. No. 3,838,966 teaches that periodate and permanganate are useful for oxidizing lower valency metal ions to their oxides. The process may be carried out in the hair to color the hair permanently. No organic dyes are used, rather the hair dyeing is by the colored metal oxides.
U.S. Pat. Nos. 3,948,596 and 3,961,879 teach the oxidation of novel aminophenols with peroxide, persulfate or perborate to color hair.
U.S. Pat. No. 3,986,825 teaches that persulfates or percarbonates may be used in a permanent waving neutralizer that also contains oxidative dyes in the setting solution. This gives concurrent permanent-waving and coloring.
U.S. Pat. No. 4,104,021 claims various compositions using perborate, periodate or percarbonate in oxidation dye mixtures incorporating a polymer/conditioner.
None of these oxidative compositions have achieved the success of hydrogen peroxide containing oxidizing compositions.
The art has long sought dye compositions which will produce colors having lasting wear quality and will not cause oxidative and bleaching damage to the hair.